The Dynamic Analysis Of Double Block Ballastless Track In Lanzhou Loess Area

With the development of high speed railway, the train speed is getting more and more faster, and has an increasing influence on the track structure and the surrounding soil and buildings. Especially in recent years, in the Loess Region where have built ballastless track, the opening of the motor train unit, such as Lanxin, Zhengxi Passenger Dedicated Line and the underconstructing Baolan line. As a kind of special soil, the loess has loose structure, the big pore, and the quite strong sensitivity to water. When the loess is used as the railway foundation, its dynamic characteristics of train load track subgrade ground system is particularly important. Especially in the existence of the loess foundation, the influence of the track subgrade system vibration.Based on vehicle-track coupling dynamics, to establish dynamic model of vehicle-track of double block ballastless. Using the Matlab programming to act on the road bed load point press fastener. The frequency spectrum analysis of the fastener load shows that the load is mainly concentrated in the low frequency, and the frequency components of the speed increase gradually move to the high frequency.Using ANSYS to establish track-subgrade-foundation finite element model. Then the fastener load as input to the model, analyzing the track bed slab vibration response, it shows that the displacement of the high frequency component is much more than that of the low frequency. At the same time, the vibration response analysis of loess foundation is carried out, which shows that the distribution law of frequency is basically unchanged. Comparative analysis on vibration response of track bed and loess foundation shows that subgrade structure has low pass filter function.The dynamic response and attenuation of track-subgrade-foundation of loess under different train speeds are compared and analyzed. It shows that the displacement is not sensitive to the change of vehicle speed with respect to the acceleration. The displacement and acceleration of ground soil increase with the increase of velocity, the attenuation of displacement and acceleration is faster firstly and the then get slower in the depth and the track.The vertical dynamic stress in subgrade surface and the fastest decay, there is the phenomenon of stress concentration at the edge of the lateral support layer. Analysis of surface layer of subgrade dynamic response with the change of elastic modulus. The results show that increases with the increase of the elastic modulus, acceleration and displacement on the surface of the are reduced.In this paper, the vibration response of Lanzhou loess is analyzed. It shows that the attenuation of the vibration in the loess decreases with the increase of the depth of the high frequency component. At the same time, considering the loess ground and not considering the Loess Foundation, The results show that the contribution of loess foundation to the vertical displacement of the track is very large, and it has little effect on the acceleration. Analysis of the when the moisture content of loess foundation rate at the same time, track subgrade foundation vibration attenuation law, indicating that with the increase of the moisture content of the loess, ground vertical displacement of the maximum value are increased, the acceleration change is not obvious.Analyzing the dynamic response of homogeneous loess under moving load, the rule of dynamic response is found as well as soft soil. When the loess is not considered, the resonance is generated near the Rayleigh wave velocity. When the damping is considered, the vertical displacement of the loess decreases with the increase of the train speed, and the acceleration increases with the increase of the train speed.